It has been a few years since my dad looked into this, (only in king and snohomish counties) we have a fullsize bassoboat and wanted to be able to fish all lakes. he got alot of runaround and was told diffrent things by diffrent people who should know. ( gamies, wdfw employees and sherrif deputies) what he understood was snohomish county will allow you to have a gas motor as long it is trimmed up( we would leave the gas tanks at home too) but king was very strict about no engines at all. but as said above one of the lakes was city ordance prohibiting engines so it is very likely one of the regulating bodies will say one thing and you could get in trouble by another. it is very confusing for us who want to be legal.